Meso/macro-porous alumina microfluidic monoliths were fabricated by an ice-templating (or freeze-casting) technique. A (green) compact with sufficient strength is obtained after controlled freezing and simple drying under ambient conditions by starting with an aqueous suspension of a mixture of submicrometer-sized α-alumina and nanometer-sized γ-alumina. A monolith with high surface area (30 m2 g−1) is obtained after sintering at 900 °C. The hierarchical structure of these monoliths consists of slit-shaped macro-pores enclosing a meso-porous skeleton with pore sizes from 20 to 60 nm. The advanced porous structure of the monoliths and their easy preparation suggests large potentials for application as flow-through catalyst support.